Take the surface of the earth. We know it's finite in area, but you can travel in a straight line anywhere on its surface and never fall off an edge, say, or bump into some kind of giant wall that lets you go no further. It's finite, but unbounded. The universe may be the same, except in three dimensions (or more) instead of two.
I would agree it has three dimensions if it were finite, as do all finite things. But wouldn't it be more accurately described as having three directions if the universe was boundless? I know, I know, just a habit saying we have a three-dimensional universe, I suppose. But is anyone here suggesting we have a measureable universe, at least in theory?
“The universe may be the same, except in three dimensions (or more) instead of two.”
Exactly the same, except that the 3 dimensional surface is an outie with the Earth, and an innie with Einie’s version of the universe.